English: Chlorine planet is a hypothetical class of planet with surface covered in lakes or oceans of muriatic acid with clouds made of muriatic acid in the atmosphere.Viewed from space, the oceans on chlorine planet would appear deep green. Lands would appear brownish to blackish green and clouds appear white with green tinge. The clouds formed when muriatic acid vapor condenses.Chlorine planets tend to be smoggy and have precipitation but no thunderstorm. Unlike Earth, chlorine planets use muriatic acid as a "variable gas" instead of water. For example, there are muriatic acid rain or muriatic acid snow instead of water rain or water snow. Chlorine planets tend to be cold, at around−110°F (−79°C), about the sublimation point of carbon dioxide. Their atmospheres tend to be composed mostly of nitrogen, oxygen, and chlorine with variable amounts of muriatic acid vapor and trace amounts of dichloride monoxide, carbon dioxide, mustard gas, and other gases.The life-bearing status on chlorine planets is fair, even though chlorine is toxic to many forms of life on Earth, but some forms of higher life somewhere in our galaxy may require chlorine to thrive. It is predicted that during the photosynthesis, muriatic acid is combined with carbon dioxide to produce formaldehyde, chlorine, and oxygen.It is also predicted that animal-like lifeforms might drink muriatic acid and eat foods rich in formaldehyde. Animals may also inhale oxygen and exhale carbon dioxide like they do on Earth. The main biogeochemical cycle on chlorine planets is the chlorine cycle compared to the carbon cycle here on Earth.